In the electronics and semiconductor industries, systems used to test and qualify integrated circuit (IC) chips during the manufacturing process are conventionally referred to as “test systems.” FIGS. 1 and 2 depict a test system 100. The test system 100 includes an electrical connector for providing an electrical connection between an IC chip 110 (which can be referred to as a “Device Under Test” or “DUT”) and a printed circuit board (PCB).
The test system 100 can include a socket body 120 defining a plurality of cavities 121. Each cavity of the plurality of cavities 121 can receive one of a plurality of spring probes 130. The test system 100 can also include a socket retainer 124.
FIGS. 3-5 depict the spring probe 130. As shown in FIG. 3, the spring probe 130 can include a shell 331, a first plunger 340, and a second plunger 350. The shell 331 can be tubular, and at least a portion of the first and second plungers 340 and 350 can be disposed within the shell 331. The socket body 120 and the socket retainer 124 can position the spring probes 130 such that the first plungers 340 electrically connect to conductive pads on the IC chip 110, and the second plungers 350 electrically connect to conductive pads on the PCB.
As shown in FIG. 4, the first plunger 340 can include a tip portion 441 that extends away from the shell 331. The first plunger 340 can also include a flange 443 that abuts the end of the shell 331 so that when a force is applied to the first plunger 340 toward the shell 331, the flange 443 pushes against the end of the shell 331 so that the first plunger 340 and the shell 331 move together. The second plunger 350 can include a tip portion 451 that extends outwardly from the shell 331.
As shown in FIG. 5, the first plunger 340 can also include a tail portion 542 inserted into the shell 331 and attached to the shell 331 (e.g., using adhesive) so that the first plunger 340 and the shell 331 move together. The flange 443 can be disposed between the tip portion 441 and the tail portion 542. The second plunger 350 can also include a tail portion 552 inserted into the shell 331. The end of the shell 331 that receives the second plunger 350 can be crimped to retain the tail portion 552 of the second plunger 350 in the shell 331 so that the tail portion 552 is slidable within the shell 331. The tip portion 451 can extend outwardly from the shell 331 away from the tail portion 552.
A spring 560 can be disposed between the two plungers 340 and 350. The spring 560 can be capable of exerting a force against each plunger 340 and 350 to bias the second plunger 350 outwardly from the shell 331 and away from the first plunger 340. The second plunger 350 can also be depressed inwardly into the shell 331 under a force directed inward against the spring 560. Thus, the first plunger 340 can be connected to the shell 331 to move with the shell 331, and the second plunger 350 can be slidable with respect to the shell 331.
FIGS. 6 and 7 depict a spring probe 630 in which both plungers are slidable with respect to the shell 331. As shown in FIG. 6, the spring probe 630 can include a shell 631, a first plunger 640, and the second plunger 350. The shell 631 can be tubular, and at least a portion of the first and second plungers 640 and 350 are disposed within the shell 331. The spring probe 630 can be positioned in the socket body 120 and the socket retainer 124 such that the first plungers 640 electrically connect to conductive pads on the IC chip 110, and the second plungers 350 electrically connect to conductive pads on the PCB.
The first plunger 640 can include a tip portion 641 that extends away from the shell 631. As shown in FIG. 7, the first plunger 640 can also include a tail portion 742 inserted into the shell 631. The end of the shell 631 that receives the first plunger 640 can be crimped to retain the tail portion 742 of the first plunger 640 in the shell 631 so that the tail portion 742 is slidable within the shell 631. The tip portion 641 can extend outwardly from the shell 631 away from the tail portion 742.
The spring 560 can be disposed between the two plungers 640 and 350. The spring 560 can be capable of exerting a force against each plunger 640 and 350 outwardly from the shell 631. Also, each of the plungers 640 and 350 can be depressed inwardly into the shell 631 under a respective force directed inward against the spring 560. Thus, the first and second plungers 640 and 350 can be slidable with respect to the shell 631.
The spring probe 130 or 630 can be formed from conductive materials, such as copper alloy coated with gold, so that an electrical connection is formed between the first plunger 340 or 640, the second plunger 350, and the shell 331 or 631. The socket body 120 and the socket retainer 124 can be formed from insulative plastic composite to insulate each of the plurality of spring probes 130 or 630 from the others.
FIGS. 8-10 depict a conventional test system 800 where a portion of the system can provide a coaxial structure. The test system 800 can include an electrical connector for providing an electrical connection between the IC chip 110 and the PCB (not shown). The test system 800 can include a top socket layer 820 defining a plurality of cavities 821, a center socket layer 822 defining a plurality of cavities 823, and a bottom socket layer 824 defining a plurality of cavities 825. The top socket layer 820 and the bottom socket layer 824 can be configured to retain a plurality of the spring probes 830 within the cavities 823 in the center socket layer 822. Also, each cavity 821 can align with one of the cavities 823 and one of the cavities 825 to accommodate one of the plurality of the spring probes 830. The spring probes 830 can be similar to either spring probes 130 or 630 described above, and can each include a shell 1031, a first plunger 1040, and a second plunger 1050.
To provide a coaxial structure, the center socket layer 822 can be formed of metal and electrically grounded. The impedance will be dependent on a diameter D1 of the inner surface of the cavities 823 of the center socket layer 822 and a diameter D2 of the outer surface of the shell 1031 of the spring probe 830.
The top socket layer 820 and the bottom socket layer 824 can be constructed from insulative plastic composite material. The top socket layer 820 and the bottom socket layer 824 do not form a coaxial structure when combined with the spring probes 130 or 630 as they are formed from insulative materials.